


Undercover Under The Mask

by Yojimbra



Category: Persona 5, Persona Series, 僕のヒーローアカデミア | Boku no Hero Academia | My Hero Academia
Genre: Crossover, Enemies to Friends to Lovers, F/M, Investigations, Midoriya Izuku is a Dork, Midoriya Izuku is a Good Friend, Multi, Mystery, Phantom Thief Midoirya Izuku, Romance, Thief Midoriya Izuku
Language: English
Status: Completed
Published: 2019-10-11
Updated: 2019-10-11
Packaged: 2020-12-09 00:51:25
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,897
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20986103
Author URL: https://archiveofourown.org/users/Yojimbra/pseuds/Yojimbra
Summary: Izuku is sent to Shujin academy to go undercover and investigate the Phantom Thieves of Hearts. He is joined by Makoto Niijima the police Investigators daughter. But as they get closer to uncovering the truths, they may find themselves swept up into the Insanity of the Phaton Thief leader Akira.





	Undercover Under The Mask

“What’s the matter, Heroboy?” The leader of the Phantom Thieves mocked. The white of her mask and red of her gloves stood out against the raging storm that had sprung out of nowhere. Her voice was sharp and filled with a wicked mirth that was reflected in her smile. 

“Can’t keep up?” She caught her dagger and flashed it at him just as thunder ripped across the sky. 

Izuku growled and pushed off of the wet floor, the area distorting around him. As he looked up at the pure black tower that the Thief was standing on. It used to be an office building. Or something. “Just turn yourself in!”

“Maybe if you catch me, Heroboy!” She jumped off the roof, arms out wide and flipping onto another building. Her laughter was maniacal and that of a true villain. For all their talk about exposing people's true hearts and being righteous, they really were just criminals. 

The investigation didn’t really matter that much anymore. He had been caught, Makoto was compromised, so there was no point in keeping things a secret. Hopefully, all of his extra training outside of class would amount to something. Calling upon One for All, he launched upward. He expected to jump off the building and climb upwards by doing the same with the building next to it. Like wall jumping.

Instead, gravity shifted when he touched the building and he was now pulled towards the building, it’s smooth black surface was his new ground. Was this some kind of quirk? Was this her quirk? Whatever it didn’t matter.

He pushed forward and gave chase, her laughter leading him through the maze of rooftops and dark skies. 

“Come on, Heroboy, you’ll never catch me like that!” She laughed, flying - no she was falling - right past him and landing on a train. For that moment he could see her smile, and her blood red eyes as she bowed at him. 

This had to be her world. Her quirk. It felt powerful.

But he wasn’t about to let her get away.

Turning on the building, he ran down it towards the ground and leapt for the train tracks. Gravity caught him and he landed on the roof of the speeding train. And she was waiting for him. Shouldn’t she be further along?

“Giving up?” He asked, One for All still crackling with energy around him. It was so strange here. 

That damn laugh was louder than the thunder as she traced her pinky along her lips. Was she trying to seduce him? “Hardly, it’s no fun if I get away that easy.” 

She held her hand up and grabbed onto a sign as it sped past. 

“Dammit!” He leapt towards the sign, barely grabbing onto it as she was already running along a street. Wait, no she was sliding on it. She was over confidant but he could use that to his advantage. 

The rain wasn’t slick as he chased after. The sky grew dark red as the buildings grew higher and higher. She lead him through an ever changing maze of buildings that had him wondering if it was a fever dream. Until she finally stopped, at the edge where the buildings gave way and a deep chasm opened up. 

It was a wound in the world. 

A nearby building fell into the pit, the sound of people screaming echoed around them. In the center of the pit, was a caged beast that feasted on the fallen building, and the only thing keeping it bound was-

“All Might?” He asked standing next to her. His breath stolen by the sight before him. Confusion wrung in his head as he stared over the abyss. Why wasn’t she running? “Were you trying to show me this?”

“This.” She held out her hand to the swirling darkness. Her voice didn’t have the mirth or joy it had moments ago as she teased him. “Is Momentos. The cognitive reality of all of Japan. Society, as a whole, believes that the only person holding back chaos is All Might. And that that seal is failing.” 

Her words rung true. All Might was the pillar that had kept their society safe. Without him, everything would crumble down. 

“Is this part of your quirk?” He asked looking her in her grey eyes. Now that she wasn’t running, he got a good look at her. Black boots that went up to her thighs where they blended with white tights, a tight waist coat bound her body and a long tailed coat with the color pressed flat against her shoulder. Her long black hair almost seemed to have a life of its own in the windless area. 

“Nah man,” A second voice said, it was a tall blond man wearing a biker’s outfit with a skull mask. “This is Momentos.”

“Ryuji?” Izuku asked blinking. “You’re a phantom thief?”

“What? Aww man? How’d you know?”

Another figure - Ann - laughed from beside him, her long blond hair in her usual pigtails and she was wearing a red leather panther suit? “No way, Ryuji, you just stand out like a sore thumb!” 

“Actually,” Makoto spoke walking along the other two. Somehow the leather, spikes, and iron mask suited her. “I think that it’s rather obvious who we are. None of our costumes are as drastic as Joker’s. Sorry, Izuku.”

“How long have you been a phantom thief?” He asked her, feeling more than a little betrayed. Did Sae know?

“About three weeks, I was there for the Kaneshiro incident.” She winced but stepped forward all the same. “But listen, this place, it’s not a place that well. Something bad is coming. And we-”

“We need your help.” Joker said and pointed towards All Might once again. “People with quirks, can’t come on here. But here you are. A hero in training. We need your help to stop whatever that thing is before it destroys all of Japan.”

XXXX

Earlier that year. Late April. 

“You wanted to see me, Sir?” Izuku asked peering into the room where All Might had asked to see him. The room was filled with several others as well, Nezu, the Principal sat on the couch sipping some tea, while Aizawa-sensei stood off to the side, talking to a woman with silver hair and red eyes. 

All Might looked up at him in his deflated form and smiled at him. “Yes, come in Izuku. Now I don’t want you to worry, you’re not in trouble, nor are you being expelled.” 

“Expelled?” Izuku stuttered as he made his way towards the seat opposite of Nezu. “What? Is this because I can’t control my quirk? I’m getting better at it Honestly I-”

“Boy!” All Might shifted into his usual spectacular self, “I said that was not the case now please sit down.”

“Yes Sir!” He did so even though now he was even more nervous as all eyes in the room were locked onto him. Especially Aizawa-sensei’s and that womans. “But umm what exactly did I get called in here for.”

“I will admit that part of it is because of your lack of control with your quirk, but we believe you can get better with time and-”

The woman stepped forward and slapped a folder onto the table. “Forgive me All Might, but you’re just making the kid worry more. Please allow me to explain.” 

“By all means, Sae.” All Might sat back and diminished his form once more. He gestured towards Sae and nodded. “Izuku, this is Sae Niijima, an investigator with the police, she has requested the aid of U.A. to help her with her case. I ask that you listen to her.”

Sae raised an eyebrow at All Might. “Why didn’t you start with that?”

All Might just shrugged.

“Now then Izuku, I’m not certain how much assistance that you’ll be able to give me, but you do fit the criteria of what I need. Let’s start with the basics.” Sae shifted open the folder and revealed two photos each of a red and black card with, wait, didn’t he recognize that symbol somewhere? “What do you know of the Phantom Thieves of Heart?” 

Oh! Them! 

“Not much Ma’am, I saw them on the internet pages a few times and a couple of my classmates talked about them. Why?” Weren’t they the group that somehow made a teacher confess with some kind of a quirk? That sounded serious because their school was a civilian school. And the teacher was a pedophile, a jerk, and asshole and absolutely deserved the punishment, but it was close to vigilantism. 

She placed down another photo, a different calling card, this one was better drawn. “They recently attacked Madarame, the artist and he revealed that he had been committing fraud for years. Because of the nature of these attacks and the way they are being committed we need to investigate and bring these thieves to justice.”

“Oh, that makes sense. But what can I do?” 

Nezu took a sip and lowered his cup. “You’ll be transferring to Shujin Academy.” 

“What?” Izuku stood up. “I thought you said that I wasn’t going to be expelled?”

“You’re not,” Aizawa-sensei took a step forward. “You’ll still be a student here at U.A. And you can return once the thieves are caught or the Shujin students are cleared. At most, you’ll be there for three months.”

“But, why me?” U.A. was his dream, he worked hard for this. So. Why him?

“Several reasons, your body still isn’t used to your quirk, giving it a bit of time to grow and adapt will do you more good than trying to force it to work now. In addition, your file still says that you’re quirkless.” He looked up to Aizawa-sensei with a gasp. His sensei just looked at him with those same dead eyes he always did. “That gives you an excuse for transferring there. To all of them, you will just be another quirkless student transferring to the school.” 

That did make sense. “But, what about my training? Won’t I fall behind the others?” 

“You’ll be gaining experience they won’t have!” Nezu cheered. “Additionally! I’d recommend joining some sports and having fun for a bit! Sports can be quite intensive! Additionally, this will open up more opportunities for you in the future! Such as internships and work study. And fear not, we’ll be certain to get you up to speed with your classmates once you return to us.”

“But I don’t have any experience with-”

“My boy,” All Might leaned forward now and produced a journal, one of his quirk study journals. “You already have a keen eye for this sort of thing. Your journal proves that you’re quite good at investigation. I know that you can do this. Working alongside the police is an important part of being a hero.”

“You won’t be alone, my sister Makoto has been tasked by her principal to also investigate this. She’s the student president. If you agree I’ll tell her about you. And the two of you can work together.”

Izuku bit his lip and stared at the papers before him. He wasn’t giving up on his dream of becoming a hero, if anything they were already asking him to do hero work. And Aizawa-sensei was right, he needed to get stronger to use his quirk. 

“Alright, I’ll do it.”

**Author's Note:**

> [Yoji's Twitter](https://twitter.com/Yoji19816784)
> 
> I'm on the Total Command discord! Come say hi! https://discord.gg/CEmYVGX


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